A novel SATB1 protein isoform with different biophysical properties

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• The Special AT-rich sequence binding protein 1 (SATB1) is a key regulator of intra-thymic T cell development.
• SATB1 orchestrates gene expression programs essential for T cell maturation.
• Dysregulation of SATB1 has been implicated in various cellular processes and diseases.

Purpose of the Study:

• To investigate the role of SATB1 in regulating transcription and splicing during T cell development.
• To characterize a novel SATB1 protein isoform and its biophysical properties.
• To explore the functional implications of SATB1 isoform diversity and its potential link to diseases.

Main Methods:

• Analysis of gene expression and splicing in Satb1 knockout murine thymocytes.
• Characterization of SATB1 protein isoforms using biophysical techniques.
• Investigation of SATB1 protein behavior, including phase separation and aggregation.
• Assessment of the impact of protein concentration, phosphorylation, and RNA interactions on SATB1 aggregation.

Main Results:

• SATB1 knockout thymocytes exhibit deregulation in transcription and splicing.
• A novel SATB1 protein isoform with distinct biophysical behavior was identified.
• SATB1 undergoes liquid-liquid phase separation and forms aggregated structures via its prion-like domains.
• The longer SATB1 isoform shows increased propensity for aggregation after phase separation.
• SATB1 aggregation is modulated by protein concentration, phosphorylation, and nuclear RNA interactions.

Conclusions:

• SATB1 isoform regulation and post-translational modifications are critical for its function in T cell development.
• Aberrant regulation of SATB1 isoforms and their behavior may contribute to the pathogenesis of diseases like cancer.
• Understanding SATB1's dynamic behavior provides insights into genome organization and gene regulation in T cells.